Chemical manufacture



Patented Jan. 2, 1940 UNITED STATES PATENT OFFICE CHEDHCAL MANUFACTURE No Drawing. Application December 18, 1937, Serial No. 180,548

5 Claims.

This invention relates to an improved process for sheening pile fabrics and more particularly pile rugs and carpets and fabrics of a like nature which are susceptible to sheening.

The process commonly known as rug sheening has for some time past been of increasing importance to the manufacturer of pile fabrics. Up to the present, no process or treatment has been developed which produces completely satisfactory results. The so-called washer method and floor method are two methods generally employed at the present time in sheening practice. The first of these involves treating the fabric in a mill at a temperature upwards of F. with a caustic solution containing bleaching powder. This solution is then removed by washing with water and the fabric is further treated with a dilute solution of bleaching powder. This step is frequently carried out by brushing for 10-15 minutes while the fabric is spread on a flat surface. After a further washing, the fabric is soured with a dilute solution of formic or acetic acid. The floor method is carried out by applying a solution containing sodium hypochlorite, prepared by passing chlorine into caustic solution, which has been heated to a temperature of upwards of 100 F. While spread on the floor, the fabric is hand brushed with the sodium hypochlorite solution. This treatment is followed by a rinse and often by an acetic acid treatment.

Operators employing these methods or variations of them have encountered numerous difficulties and found that they possess many serious disadvantages. Outstanding among these have been the inability of these methods to give reproducible results. This is a particular disadvantage in the manufacture of carpets where a certain pattern and finish must remain substantially uniform throughout a large quantity of material which is manufactured over a long period of time. For various reasons which are more fully discussed below, it has been very difficult if not impossible to obtain a constant sheen and a uniform shade of color by the use of the methods of sheening known to the art. In many cases it has been found that a treatment appropriate to produce the desired sheen also causes a loss or fading of the color in the fabric and frequently introduces an entirely different tint in the desired color. A further outstanding difficulty has been that a serious loss of tensile strength of the fibers often accompanies the sheening process. This of course greatly reduces the life of the fabric by lowering its resistance to wear. Certain of the known methods have been found to possess a tendency to remove the twist from the yarn thus making sheening difficult and causing the finished product to have an undesirable fuzzy appearance. This tends to disturb the original demarkations in the patterns. Further disadvantages which the proposed methods of sheening have failed to overcome are the running together of colors in pattern fabrics, 1 uneven or streaky sheening, and a variation in color or degree of sheen from the top of the pile to the bottom.

It is the primary object of the present invention to provide a chemical method of pile fabric 35 sheening which will eliminate or minimize the above-recited difficulties and disadvantages which attend the use of the methods known to the art. The process of the present invention accomplishes this by providing a chemical treatment which produces a minimum loss of fiber strength and at the same time produces a uniform maximum sheen without altering or destroying the color or the texture of the fabric. This invention, furthermore, provides a process which is easily operated and controlled.

We have found that the above-recited ends may be attained and the disadvantages hitherto involved either eliminated or minimized by subjecting the pile fabric to a two-stage treatment followed by an acid souring treatment. The initial stage of our process comprises treating the fabric for a limited period of time with a dilute caustic solution at approximately room temperature. Subsequent to a rinsing operation the fabric is then treated with a dilute but well regulated solution of calcium hypochlorite. This calcium hypochlorite solution is with special advantage substantially free of calcium chloride and of minimum lime content. The fabric is again rinsed and then subjected to a .dilute formic or acetic acid wash to complete the sheening process. The present process may be carried out in any apparatus suitable for subjecting fabrics to successive treatments in different solutions with intermediate rinses.

Wool fiber is composed of a cortex covered with epithelial scales. It is well known that chemical treatment of wool fibers is hazardous. While we are unable to state definitely the course of the chemical reaction occurring be- 0 tween a substance such as bleaching powder and a wool fiber, it appears that the imbricated or serrated surface of the fiber is first attacked and the protecting scales removed. This exposes the fibrous material itself to the destructive action of the, chemicals in the treating solution and the resulting damaged fiber is unsatisfactory for many purposes, including use in pile fabrics. We have found that the improved two-stage sheening process herein described does not destroy the epithelial scales or attack the fiber directly and that the disadvantages attendant upon such destructive action are therefore obviated. While we are unable to state definitely the reasons for the improved results obtained by the use of'the herein-described procedure, it would appear that the reaction taking place is a very limited one which tends to change the imbricated surface of the fiber to a relatively smooth surface which has an increased tendency to directly reflect rather than scatter light rays. In this way the desired sheen is imparted to the fabric. It is to be understood, however, that our invention is not limited to any particular hypothesis as to the mechanism of the process.

In the initial stage of our improved sheening process the pile fabric is subjected to treatment in a solution of alkali such as caustic soda. The proper concentration of this alkali solution to be used is best determined by experiment. tions in color and weight of the fabric undergoing sheening result in a variation of the alkali concentration which produces best results. In general we have found that a concentration of approximately 3.5 grams per liter results in maximum efiiciencies, while concentrations somewhat above or below this figure may often be employed with advantage. Solutions having caustic alkali concentrations up to about 6 grams per liter have been employed without causing a significant loss of tensile strength in the fiber. There is a maximum caustic concentration beyond which the operation should not be conducted since the fiberisfattacked and a loss in tensile strength and wearing properties occurs due to the action of the alkali. We have found that in most cases a treating time for this caustic treating step of approximately 15 minutes is most desirable. Best .results have been obtained with temperatures in the region of room temperatures which may range from approximately 45 F. to F. A temperature approximately 65 F. is preferred at this stage of the process.

Following the alkali treatment the fabric is advantageously given a water rinse of from 2 to 5 minutes at about 90 F. It is then subjected to a treatment in a solution of calcium hypochlorite, the treatment being of approximately the same duration as the alkali treatment.

To obtain the full benefits of the process of the present invention, the calcium hypochlorite should be substantially free of calcium chloride and should contain a minimum of free lime. The presence of free lime in the second or hypochlorite stage of the process sometimes tends to increase the sheen obtained, but if present to excess frequently causes undesirable changes in the color of the fabric. Calcium hypochlorite compositions prepared as described in United States Letters Patent No. 1,787,048, granted to Robert B. MacMullin and Maurice C. Taylor on an application filed August 16, 1928, are particularly useful in the process of the present invention. Such calcium hypochlorites are not to be confused with conventional bleaching powder or chlorinated lime. They differ materially from bleaching powder or chlorinated lime both in chemical constitution and in content of available chlorine. Instead of being a complex compound Variaincluding chloride and hypochlorite, they are true calcium hypo'chlorites. The difference in available chlorine content, however, is more readily determined than is the more fundamental difference in chemical constitution. Characteristically such calcium hypochlorites contain upwards of 50% available chlorine and, with advantage with respect to this invention, upwards of 60% available chlorine.

The concentration of the calcium hypochlorite which gives the best results is even more dependent on the type, weight and color of the fabric being sheened than is the alkali concentration in the first stage of the process. In most cases, we have found that a solution having an available chlorine content ranging from 0.75 to 3.0 grams per liter is desirable, the exact amount depending largely on the fabric undergoing treatment. In certain special cases concentrations of available chlorlne somewhat above or slightly below these concentrations may prove desirable. These concentrations have been found to fall within the available chlorine concentration range of 0.5 to 5.0 grams per liter. With fabrics of the same weight but of different colors we have found that the desirable concentration varies and that a concentration preferred for one sample may be too great for use on a fabric which has the same.

properties except for color. In such cases an undesirable tint is often added to the original color. The concentration which gives optimum results with respect to color and sheen accompanied by a minimum loss of tensile strength of the fiber is therefore, as in the case of the caustic in thefirst step, best determined by experiment. Here again the concentrations, in this case of available chlorine supplied by the calcium hypochlorite, which are necessary to produce the best results with respect to color and sheen, are considerably below the concentration at which fiber .degradation is significant. For best results the hypochlorite solution must be substantially free from calcium chloride and of low lime content.

The temperature. of the solution during the hypochlorite treatment is advantageously maintained at a slightly higher value than that of the caustic solution. This may range from about 50 F. to F., but we have found that a temperature of about 90 F. is particularly efiicient. The temperatures employed in both steps of our process are lower than those employed in the previously known methods of sheening to which reference has been made.

Following the hypochlorite treatment the fabric should be given a water rinse similar to the previous one and subjected to a souring treatment. Formic or acetic acids of sufficient concentration to cause the treating solutions to have a slightly acid reaction to litmus may be employed in this step.

The following specific examples will serve to more fully illustrate the practice of the present invention, but they are not presented as any limitation on the scope of the invention. The fabrics used in these tests were rugs manufactured by a commercial rug manufacturer. The rugs were cut into 6-inch squares and treated under widely varying conditions in order to determine the conditions giving the best results.

A Wilton rug having a green color and of medium weight was placed in 3 liters of a solution containing 3.5 grams caustic soda per liter and having a temperature of 65-'70 F. After being in contact with this solution for 15 minutes the rug was rinsed for 5 minutes in water at a temperature of 90 F. It was then placed in 3 liters of a solution of calcium hypochlorite of the above recited properties. This solution had an\ available chlorine concentration of approximately 1 gram per liter and was maintained at a temperature approximating 90 F. After a period of 15 minutes the sample was again rinsed and soured in a formic acid solution. As a result of this treatment the rug had attained a high degree of sheen, maintained the same color and suiiered a negligible reduction in tensile strength. In this case an increase in the available chlorine concentration of the hypochlorite solution introduced a yellow tint in the original color.

Another sample having a blue color was treated substantially as just described, except that with this rug a concentration of available chlorine of 1.5 grams per liter was found necessary to produce the best results. Concentrations above this value caused a greenish cast to appear in the blue color.

Another sample having a color known as eggplant was treated in a similar manner but in this case a concentration of available chlorine equal to 2 grams per liter was found to give the best results. Above this value a reddish tinge was in troduced.

While full advantage of the process of this invention is to be obtained only by using in the second stage calcium hypochlorite as previously distinguished from bleaching powder or chlorinated lime, the two-stage operation of the invention affords some advantages even though bleaching powder or chlorinated lime is used in the second stage. Since the available chlorine content of bleaching powder or chlorinated lime is low, larger proportions of it must be used to produce a solution containing the same available chlorine content. With this change the process of the invention substituting bleaching powder or chlorinated lime for calcium hypochlorite in the second stage may be carried out as previously described. As distinguished from bleaching powder or chlorinated lime, calcium hypochlorites give a somewhat better sheen, leave a tighter pile and do not have as much tendency to take the twist out of the yarn and give a better strength retention and a better tensile strength.

We claim:

1. The method of sheening the pile of wool rugs which comprises subjecting the pile to treatment in an aqueous caustic alkali solution in which the alkali concentration is insufficient adversely to afiect the pile, and thereafter subjecting the pile to treatment in an aqueous solution or calcium hypochlorite,' the concentration of available chlorine in said solution} being insufficient to cause a substantial loss of tensile strength of the fiber and insufiicient to alter the color of the pile.

2. The method of sheening the pile of wool rugs which comprises subjecting the pile to treatment in an aqueous caustic alkali solution in which the alkali concentration is insuflicient adversely to affect the pile, and thereafter subjecting the pile to treatment in an aqueous solution having dissolved therein calcium hypochlorite containing upwards of 50% available chlorine, the concentration of available chlorine in said solution being insuificient to cause a substantial loss of tensile strength of the fiber and insufficient to alter the color of the pile.

3. The method of sheening the pile of wool rugs which comprises subjecting the pile to treatment in an aqueous caustic alkali solution having an alkali concentration of not more than 6 grams per liter, and thereafter subjecting the pile to treatment in an aqueous solution having dissolved therein calcium hypochlorite containing upwards of 50% available chlorine, the concentration of available chlorine in said solution being within the range of 0.75 gram to 3 grams per liter, but less than an amount sufiicient to introduce an appreciable loss of tensile strength in the fiber and less than an amount sufficient to alter the color of the pile.

4. The method of sheening the pile of wool rugs which comprises subjecting the pile to treatment in an aqueous caustic alkali solution having an alkali concentration of not more than 6 grams per liter and a temperature within the range of about F. to about 90 F., and thereafter subjecting the pile-to treatment in an aqueous solution having dissolved therein calcium hypochlorite containing upwards of available chlorine, the concentration of available chlorine in said solution being within the range 0.75 gram to 3 grams per liter, but less than an amount sufficient to introduce an appreciable loss of tensile strength in the fiber and less than an amount suflicient to alter the color of the pile, said hypochlorite solution being maintained at a temperature within the range of about 50 F. to about 120 F.

5. The method of sheening the pile of wool rugs which comprises subjecting the pile to treatment in an aqueous caustic alkali solution in which the alkali concentration is insufficient adversely to affect the pile, and thereafter subjecting the pile to treatment in an aqueous solution of bleaching powder, the concentration of available chlorine in said solution being insufficient to cause a substantial loss of tensile strength of the fiber and insufilcient to alter the color of the pile.

JAMES DOUGLAS MAcMAHON. VARTON MARDIRAS KALUSDIAN. LORENZO D. TAYLOR. 

